Peripheral Protein Organization and Its Influence on Lipid Diffusion in Biomimetic Membranes

Abstract

Protein organization on biomembranes and their dynamics are essential for cellular function. It is not clear, however, how protein binding may influence the assembly of underlying lipids or how the membrane structure leads to functional protein organization. Toward this goal, we investigated the effects of annexin a5 binding to biomimetic membranes using fluorescence imaging and correlation spectroscopy. Annexin a5 (anx a5), a peripheral intracellular protein that plays a membrane remodeling role in addition to other functions, binds specifically and tightly to anionic (e.g., phosphatidylserine)-containing membranes in the presence of calcium ion. Our fluorescence microscopy reveals that annexin likely forms assemblies, along with a more dispersed population, upon binding to anionic biomembranes in the presence of calcium ion, which is reflected in its two-component Brownian motion. To investigate the effects of annexin binding on the underlying lipids, we used specific acyl chain-labeled phospholipid analogs, NBD-phosphatidylcholine (NBD-PC) and NBD-phosphatidylserine (NBD-PS). We find that both NBD-labeled lipids cluster under anx a5 assemblies, as compared with when they are found under the dispersed annexin population, and NBD-PS exhibits two-component lateral diffusion under the annexin assemblies. In contrast, NBD-PC diffusion is slower by an order of magnitude under the annexin assemblies in contrast to its diffusion when not localized under anx a5 assemblies. Our results indicate that upon binding to membranes, the peripheral protein annexin organizes the underlying lipids into domains, which may have functional implications in vivo.

Folding and Lipid Composition Determine Membrane Interaction of the Disordered Protein COR15A

“…Despite this, COR15A binding to ICMM resulted in a significant reduction in the rate of lateral diffusion of all three lipid species. This is in agreement with experimental studies of the effect of binding of annexin a5 and a-synuclein on lateral lipid diffusion (68,69). In addition to the reduction in lateral diffusion, we also found a significant reduction in the compressibility modulus of the ICMM membranes upon binding of COR15A, indicating a less-rigid bilayer.…”

Monte Carlo Simulation of Protein-Induced Lipid Demixing in a Membrane with Interactions Derived from Experiment

“…1 D and Fig. 2, light gray bars), which were observed experimentally by fluorescence microscopy (55). Fig.…”

“…This variation of ε A results in going from very small clusters (dominated by single proteins) to very large ones (essentially one large domain) over a range of only 50 cal/mol. If ε A % -0.8 kcal/mol (more negative), complete agglutination of the protein on the membrane results, which was not observed experimentally (55).…”

Analysis of CD44-Hyaluronan Interactions in an Artificial Membrane System

“…This is particularly so for the His-HABD monomer, which is anchored by a single (or at most very few) bis-NTA lipid to the fluid lipid membrane. In the case of the doubleheaded (HABD) 2 -Fc construct, the AnxA5 anchors are also likely to be laterally mobile under the conditions employed here (26,45), although their dense packing may slow down large scale lateral motions.…”